The graph shows the spacecraft paths in the geocentric mean equator and equinox of J2000 reference frame.

The three lines are for the initial spacecraft position shown in the graph (2004-03-02 09:25:18 UTC): the blue line represents the instantaneous Earth's heliocentric velocity vector, the yellow line points toward the Sun (both lines lie almost exactly in the J2000 ecliptic plane) and the gray line points toward the Moon.

The popup label that appears when you hover the mouse over a black dot (the spacecraft hyperbolic escape orbit) shows the UTC time, the spacecraft radius vector (km) and the spacecraft geocentric inertial speed (km/s).

The graph seems to show that Rosetta is fast moving toward the Sun, but it's not true; please, take a look at the next graph.

Here's the same graph as the above, but the reference frame is the heliocentric mean ecliptic and equinox of J2000 (the Sun position is x = 0, y = 0 and z = 0).

The black small dots represent the spacecraft, the blue dots represent the Earth and the gray dots represent the Moon.